Shortened R12 Driveshafts
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  1. #1
    Fellow Frogger! Virage Racer's Avatar
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    Default Shortened R12 Driveshafts

    Hi R12 Gurus

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    My Virage is fitted with an R18 5 speed box and the previous owner had 'shortened' the driveshafts (about 0.5 inch, I believe) to compensate for the greater width of the box and the shorter distance between drive pinion and front hubs.

    However, 'shortening' seems a bit of a misnomer. When the 'shortened' shaft is compressed all the way and compared to a standard shaft, it definitely is shorter. But at full extension, it seems to be the same length as a standard shaft. Does that mean the inner CV is able to slide further towards the axle centre on the 'shortened shaft' (ie longer travel) rather than a physical relocation of the inner yoke on the shaft?

    The reason this has come up is that I'm about to introduce some neg. camber on the front by fitting longer lower wishbones (+ 0.5 inch) and I'm trying to work out whether this means going back to standard driveshafts.

    If necessary, I'll start peeling back boots and doing forensics, but I'm just wondering if anyone is familiar with how the driveshaft mod is carried out.

    Cheers
    Keith
    1976 12 Gordini Faker
    WA's only 12 in regular club comp

  2. #2
    Simon's Avatar
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    Probably post up a picture of the driveshaft, it will help identifying the type of joints on each end (4 ball Bendix, GE 86 spider etc) also it may give a clue as to how it was modified, as the few that I have seen have been sleeved to shorten them. Iíd imagine there may be a number of ways that others have done the same conversion.

    Technically, you would only want to shorted it so that it operates in a similar range of the driveshaft as the original, so I canít really see how it could be shorter on compression, but just as long if extended, unless the inner joint is at the very limits of its extension, just that it isnít obvious from the outside.

  3. #3
    Fellow Frogger! MARK BIRD's Avatar
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    Default Drive shaft shortening

    In shortening a drive shaft the best way is to reduce your length from the very end Depending on design you would press the joint end off this will reveal the splines a hardness test would need to be done and annealling of the end to enable machining back of shaft to desired length then new splines cut . When this is done shaft can be hardened back to specification and reassembled.
    Check with what simon is giving you in the way of driveshaft types but if you are really worried and want to know in absolute terms where the shafts sit in relation to your car measure your total wheel travel and remove the spring ( I know its not a easy task on a R12 without the Renault patent tool ) Pick a drive shaft for use as a template and remove all boots so you can physically see the position the joints sit in relation to suspension movement and with a jack under the lower arm move the suspension to max and min travel
    Last edited by MARK BIRD; 29th November 2005 at 08:55 PM.

  4. #4
    1000+ Posts alan moore's Avatar
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    An EA Falcon camber kit (was available cheaply from Ford )can be fitted to the upper wishbone to allow more negative camber. It still requires some slotting of the holes where the wishbone bolt goes, but fits like it was made for it. I fitted these to my 15.

    Mark is on the right track about resplining, then hardening the inner end of the driveshaft to shorten it. Maybe 18 driveshafts are the answer. The outer splines are the same as a 12, and the inner would fit the std 18 box without changing over the output parts of the gearbox to R12, don't know about the length.
    '56 Renault 750 (16TS Power)
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  5. #5
    Fellow Frogger! Covert's Avatar
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    Quote Originally Posted by Virage Racer
    Hi R12 Gurus
    The reason this has come up is that I'm about to introduce some neg. camber on the front by fitting longer lower wishbones (+ 0.5 inch) and I'm trying to work out whether this means going back to standard driveshafts.
    If necessary, I'll start peeling back boots and doing forensics, but I'm just wondering if anyone is familiar with how the driveshaft mod is carried out.
    Cheers
    I know this may not be of any help, but on my R15 I have a R18 box in it (easy to blow up over a TS/G box), I bought it off a guy who had played with it..... and told me he had used R16 splines in the box instead of the R18 units sitting out the side of the box, they where shorter and thus it allows you to run standard R15/17 drive shafts, so you don't need cut shafts.

    Now I am not a technical measurement person, but maybe that can help you coming around the problem in a different way, maybe simon may know the spec difference of a R16 spline that sits out the side of the box and a R18 one on his microfiche ....

    I hope I have these terms right

  6. #6
    Simon's Avatar
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    Quote Originally Posted by Covert
    and told me he had used R16 splines in the box instead of the R18 units sitting out the side of the box, they where shorter and thus it allows you to run standard R15/17 drive shafts, so you don't need cut shafts.
    Yep, that's the other way of approaching the same problem without cutting the shafts. So it will be interesting if using the stock 18 gearbox with its longer output shafts, if the stock 12/15/17 driveshafts can be run with the negative camber kit.

    If Alan Moore had the camber kit on his 15 with the stock driveshafts, and the stock gearbox, the shortened driveshafts may still be OK, or even stock 12/15/17 ones may suit. As has been suggested though, probably a dry run with a bare driveshaft is the best way to test things out.

  7. #7
    1000+ Posts alan moore's Avatar
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    On my 15 I had previously slotted the lower wishbone mounting holes and then welded 50 x 50 x 3 mm plates over this to strengthen the arrangement. What I did not explain very well was that R12 (and I expect R16) output parts can be fitted to the 18 box so that the std 12/15 driveshaft can be used. I have seen this done, and I can't remember any shaft shortening necessary.

    The inside joint is apparently stronger on the 15/17 driveshaft, but I only broke a 12 one when an engine mount broke and allowed the engine to twist and lift. If enough power is applied, the weight just tranfers and the wheel spins limiting Hp through the driveshaft.
    '56 Renault 750 (16TS Power)
    '62 Renault Dauphine Gordini
    '89 Renault Alpine GTA V6 Turbo
    '08 Renault Megane sedan

  8. #8
    Simon's Avatar
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    Quote Originally Posted by alan moore
    but I only broke a 12 one when an engine mount broke and allowed the engine to twist and lift.
    Was this the nice orange 15 at Jugiong back in 1987??

  9. #9
    Fellow Frogger! Virage Racer's Avatar
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    I think, as has been suggested, forensics are the only way to find out what has been done to the shortened shafts. The idea of using a bare shaft and studying what the joints are actually doing during the full travel of the suspension is also a good one.

    In the discussion I'm getting a bit confused over whether it's the upper or lower wishbones which will accept the EA Falcon camber pin kit. I had expected to get both a wider track and neg camber by extending the lower wishbones, but being able to make fine adjustment of camber using the upper wishbone seems like a useful future mod. I presume this was an aftermarket kit offered by one of the suspension specialists?

    Cheers
    Keith
    1976 12 Gordini Faker
    WA's only 12 in regular club comp

  10. #10
    Fellow Frogger! MARK BIRD's Avatar
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    Quote Originally Posted by Virage Racer
    I think, as has been suggested, forensics are the only way to find out what has been done to the shortened shafts. The idea of using a bare shaft and studying what the joints are actually doing during the full travel of the suspension is also a good one.

    Cheers
    Especially if you are rallying the car with its extremes of travel.

  11. #11
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    mistareno's Avatar
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    As was posted re the R16 output shaft splines...

    I used an 18 5 speed box in my old 12 and I had the box split and had the 18 output shafts (and the differential adjuster/seal retainer) replaced with R12 ones. (the 18 box seals on the output shaft whereas the 12 box seals on the drive shaft)

    The R12 diff housing itself is the same part number as the R18 box so it is a straight swap and the box is then the same width as a standard R12 box which means you can use unmodified R12/17 driveshafts.

    It is a bit of an initial expense to get the box split, but once done, it all looks stock and shouldn't give any problems...

  12. #12
    1000+ Posts alan moore's Avatar
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    Simon,
    Yes that was my 15 at Jugiong. I sold it in '90 when a bought a 205GTI, and then bought it back again a few years later.

    The Camber adjusters were a Ford part to help solve the front end problems in the EA. Way back then the kit was $30 to do both sides. They fit to the top arm of a 12/15/17. I was running 2.5 degrees of negative camber for road use.
    '56 Renault 750 (16TS Power)
    '62 Renault Dauphine Gordini
    '89 Renault Alpine GTA V6 Turbo
    '08 Renault Megane sedan

  13. #13
    Fellow Frogger! Virage Racer's Avatar
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    Thanks Richard

    I'd heard about the 12 output parts on the 18 box mod, but getting a wider track is also part of the object of the exercise.

    I've had to give up on mods and reassemble the way things were for an autokhana this weekend, so more later as I get a chance to resume.

    Cheers
    Keith
    1976 12 Gordini Faker
    WA's only 12 in regular club comp

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